class Solution {
    int dx[4] = {0, 0, 1, -1};
    int dy[4] = {1, -1, 0, 0};
    bool vis[25][25];
    int m, n, ret;
 
public:
    int getMaximumGold(vector<vector<int>>& grid) {
        m = grid.size(), n = grid[0].size();
        for(int i = 0; i < m; ++i)
        {
            for(int j = 0; j < n; ++j)
            {
                if(grid[i][j] != 0)
                {
                    vis[i][j] = true;
                    dfs(grid, i, j, grid[i][j]);
                    vis[i][j] = false;
                }
            }
        }
        return ret;
    }
 
    void dfs(vector<vector<int>>& grid, int i, int j, int sum)
    {
        ret = max(ret, sum);
        for(int k = 0; k < 4; ++k)
        {
            int x = i + dx[k], y = j + dy[k];
            if(x >= 0 && x < m && y >= 0 && y < n && grid[x][y] != 0 && !vis[x][y])
            {
                vis[x][y] = true;
                dfs(grid, x, y, sum + grid[x][y]);
                vis[x][y] = false;
            }
        }
    }
};